Grinding machine

ABSTRACT

This invention relates to a grinding machine and, more particularly, to apparatus for forming a surface of revolution by the abrasion process making use of the controlled-force principle.

United States Patent [191 Klar [ Apr. 16, 1974 1 GRINDING MACHINE.

[75] Inventor: John Klar, West Boylston, Mass.

[73] Assignee: Cincinnati Milacron-Heald Corp.,

Worcester, Mass. Y

22 Filed: July 20, 1972 21 Appl. No.: 273,641

Related US. Application Data [63] Continuation-impart of Ser. No. 63,704, Aug. 14,

1970, abandoned.

[52] US. Cl. 51/98 R, 51/103 R, 51/165.76, 51/165.79, 51/165.89, 51/165.93

[51] Int. Cl..... B24b 5/10, B24b 47/20, B24b 47/22 [58] Field of Search 51/98 R, 100 R, 101 R, I 51/103 R, 105 R,131',165.76,165.79,

[5 6] I References Cited UNITED STATES PATENTS 8/1971 Robillard 51/165.8

Robillard 51/165.91

3,691,699 9/1972 Uhtenwoldt 51/165.8 3,404,490 10/1968 Estabrook 318/432 X 2,647,348 8/1953 Hahn 5l/165.8 3,605,344 9/1971 Hahn 51/165.8 X 3,197,921 8/1965 Hohler... 51/165.93 X 3,131,517 5/1964 Townsend.. 51/165.93 909,300 1/1909 Hirth 51/165.79 1,754,140 4/1930 Asbridge.... 51/165.79 1,683,859 9/1928 Brown 51/165.77

OTHER PUBLICATIONS A. Kalenian, Torque-Motor Drive," Product Engineering, Nov. 13, 1961, pp. 105-107.

Primary ExaminerDona1d G. Kelly Attorney, Agent, or Firm-Norman S. Blodgett [5 7] ABSTRACT This invention relates to a grinding machine and, more particularly, to apparatus for forming a surface of revolution by the abrasion process making use of the controlled-force principle.

7 Claims, 8 Drawing Figures I MENTEI] APR 1 8 i974 240 V, 60 CPS AU TOTRA NSF ORMER a H o 0 MOTOR FIELD CAPACITOR I VARIABLE 7 REACTOR F I G. 5

FIELD VARIABLE REACTOR CAPACITOR FIG. 6

SHEEI 2 0F 2 r L f 7" I AUTDTRANSFORMER5 F l G. 7

:FIELD AUTOTRANS- CAPACI TO AUTOTRA NSFORMER/ GRINDING MACHINE CROSS-REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of U.S., now abandoned Pat. application Ser. No. 63,704 filed Aug. 14, 1970.

BACKGROUND OF THE INVENTION The controlled-force principle of grinding has proved to be very useful, particularly in internal grinding applications. When the force between the grinding wheel and the workpiece is maintained at a constant value during a given portion of a grinding cycle from workpiece to workpiece, the deflection of the spindle remains the same and the selected angularity between the wheelhead and the workhead will remove any possibility of taper in the finished bore. Furthermore, control of the force allows one to operate at a grinding pressure which is the maximum that the wheel will allow, and this can be done without the danger of exceeding this value. Furthermore, during certain portions of the grinding cycle, a suitable force can be selected which will give the optimum surface finish to the workpiece surface. In the past, however, this selected or controlled force has been brought about by using a feed element having pressure fluid as its medium. A feed mechanism of this type can be space-consuming, complicated, and expensive because of the conduits and valves involved in the control of the fluid. These and other difficulties experienced with the prior art devices have been obviated in a novel manner by the present invention.

It is, therefore, an outstanding object of the invention to provide a grinding machine having electrical means for producing controlled-force grinding.

Another object of this invention is the provision of a grinding machine having a cross-feed apparatus using a constant-torque D.C. electric motor, where the speed of said motor has no bearing.

A further object of the present invention is the provision of a grinding machine using the controlled-force principle wherein the feed mechanism requires no hydraulic valves and conduits.

With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set fotth in the specification and covered by the claims appended hereto.

SUMMARY OF THE INVENTION In generahthe invention relates to a grinding machine for generating a surface of. revolution on a workpiece having a base, having a workhead for carrying the workpiece mounted on the base, and having a wheelhead having a spindle with an abrasive wheel mounted on the base. Ways are provided for permitting sliding motion transversely of the spindle axis between the workhead andthe wheelhead to cause an engagement of the abrasive wheel with the surface of revolution of the workpiece. A constant-torque motor system is provided with connection means joining the output shaft of the motor to one of the wheelhead and workhead to produce constant force engagement of the wheel and workpiece.

BRIEF DESCRIPTION OF THE DRAWINGS The character of the invention, however, may be best understood by reference to one of its structural forms, as illustrated by the accompanying drawings, in which:

FIG. 1 is a perspective view of a grinding machine embodying the principles of the present invention,

FIG. 2 is a perspective view of a modified form of the grinding machine, 7

FIG. 3 is a plan view of a portion of the machine taken on the line Illlll of FIG. 2,

FIG. 4 is a schematic view of a motor system, and

FIGS. 5-8 show variations of the motor system.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring first to FIG. 1, the grinding machine, indicated generally by the reference numeral 10, is shown as having a base 11 on which is mounted a workhead 12 and a wheelhead 13. The workhead'carries and rotates a workpiece 14 having a bore to be finish ground and the wheelhead has a spindle 15 carrying at its outer end anabrasive wheel 16.

Ways 17 are provided between the base 11 and the workhead 12 to permit the workhead to be moved longitudinally of the axis of the spindle 15. Ways 18' are provided to permit sliding motion of the wheelhead 13 transversely of the spindle axis to bring about an engagement of the abrasive wheel 16 with thesurface of revolution 19 of the workpiece 14.

Aconstant-torque motor system 21 is-mounted on a portion of the base 11 and connection means 22 is provided for joining the output shaft 23 of a motor 24 to the wheelhead 13 to provide constant force engagement of the wheel and workpiece.

A connection means 22 consists of a loop 25 of cable having at least one wrap around the said output shaft 23 of the motor 24. The loop lies in a plane perpendicular to the spindle axis, extends around four pulleys 26, 2'7, 28, and 29 which are mounted on the base, and has one run 31 between the pulleys 26 and 28 that is attached to the wheelhead 13.

The motor system 21 is of the type known as the CAPACITRON manufactured by the Vee-Arc Corporation of Westboro, Massachusetts shown and described in the Nov. 13, I961 issue of Product Engineering Magazine. As such, it consists of a source of direct current power and inductance having an INDEPEND- ENTLY-excited field, a capacitance, a motor 24, and connections joining the power source, the capacitance, and the motor in series. More specifically, the armature isenergized with DC. from a rectifier whose A.C. input is in series with continuous duty capacitors; the voltage automatically adjusts itself to the load. A typical circuit is'shown in FIG. 4. This motor has the capacity of providing a constant-torque output at all speeds to zero RPM or a stalled condition.

The operation of the invention will now be readily understood in view of the above description. The movement of the workhead 12 over the ways 17 provides the longitudinal motion between the workpiece 14 and the abrasive wheel 16', while the movement of the wheelhead 13 over the ways 18 provides for the transverse or feed motion. The feed motion takes place by means'of the motor 24 which is operated at a constant-torque value which can be pre-selected to give a desired constant force pulling of the cable 22. This produces a constant force engagement in the transverse direction between the abrasive wheel 16 and the surface of revolution 19 of the workpiece 14.

FIG. 2 shows a modified form of the invention, including a grinding machine 32 having a base 33 having longitudinal ways 34 on which are mounted a workhead 35 carrying a workpiece 36 for longitudinal motion thereof. Also mounted on the base 33 are ways 37 carrying a wheelhead slide 38 on the upper surface of which is mounted a wheel head 39 which is driven by a motor 41. The wheelhead has a spindle 42 at the outer end of which is provided an abrasive wheel 43. Mounted on a portion of the base 33 is a motor system 44 having a motor 45. The motor is arranged on the base 33 with its output shaft 46 extending at a right angle to the spindle axis. At its outer end, the shaft is provided with a small gear 47 which is engagable with the periphery of a large gear 48. It is mounted for rotation about an axis perpendicular to the spindle axis by means mounted on the base 33 but not shown for the purpose of clarity of presentation. The side of the gear 48 opposite the motor 45 is provided with a cam 49 as is evident in FIG. 3. The cam has an operative surface 51 and engages and slides relative to a pin 52 which extends horizontally from the front face of the wheelhead slide 88. This cam, of course, is rotatable about an axis spaced from and parallel to the pin and the operative surface 51 of the cam is an inclined ramp concentric with the cam axis and facing the pin. This surface, if unwrapped and straightened out, would be a simple straight line wedge and, therefore, serves to press the pin 52 and the wheelhead table slide 38 rearwardly at a constant speed and, because the motor system 44 is of the constant-torque type described above, it is able to rotate only at constant-torque. That is to say, the speed of rotation of the cam 48 may vary somewhat, but the force transmitted to the pin 52 remains at a constant value, so that controlled-force feeding of the grinding machine takes place in the desirable manner.

FIG. shows another constant-torque motor system that can be used in connection with the present invention; in this modification of the motor system a variable reactor is used with a series-wound AC-DC motor. In FIG. 6 is shown a constant-torque motor system in which a variable reactor is used with a shunt'wound DC motor. FIG. 7 shows a constant-torque motor system having a variable transformer and a fixed reactor used with a shunt-wound DC motor. FIG. 8 shows a variation of the motor system shown in FIG. 7; autotransformer and a variable capicator in parallel are used in place of the variable capicator alone.

It can be seen, then, that, by use of the present apparatus, it is possible to provide a constant force grinding machine wherein the apparatus for control is quite simple. All of the equipment is electrical, and there is no need for bulky conduits and valves; operation can take place by the use of simple switches.

It is obvious that minor changes may be made in the form and construction of the invention without departing from the material spirit thereof. It is not, however, desired to confine the invention to the exact form herein shown and described, but it is desired to include all such as properly come within the scope claimed.

The invention having been thus described, what is claimed as new and desired to secure by Letters Patent l. A grinding machine for generating a surface of revolution on a workpiece, comprising a. a base,

b. a workhead element for carrying the workpiece mounted on the base,

c. a wheelhead element having a spindle with an abrasive wheel mounted on the base,

d. way means permitting sliding motion transversely of the spindle axis between the workhead and the wheelhead to bring about engagement of the abrasive wheel with the surface of revolution of the workpiece,

e. a constant-torque rotary motor system having a rotatable output shaft, the system including means to maintain the torque on the shaft at a predetermined value, and

f. connection means joining the output shaft of the motor to one of the elements to produce constant force engagement of the wheel and workpiece.

2. A grinding machine for generating a surface of revolution on a workpiece, comprising a. a base,

b. a workhead element for carrying the workpiece mounted on the base,

c. a wheelhead element having a spindle with an abrasive wheel mounted on the base,

d. way means permitting sliding motion transversely of the spindle axis between the workhead and the wheelhead to bring about engagement of the abrasive wheel with the surface of revolution of the workpiece,

e. a constant-torque motor system, and

f. connection means joining the output shaft of the motor to one of the elements to produce constant force engagement of the wheel and workpiece, the said connection being a loop of cable having at least one wrap around the said output shaft of the motor, and the loop lying in a plane perpendicular to the said spindle axis, extending around four pulleys mounted on the base, and having one run between pulleys attached to the said one of the elements.

3. A grinding machine for generating a surface of revolution on a workpiece, comprising a. a base,

, b. a workhead element for carrying the workpiece mounted on the base,

c. a wheelhead element having a spindle with an abrasive wheel mounted on the base,

d. way means permitting sliding motion transversely of the spindle axis between the workhead and the wheelhead to bring about engagement of the abrasive wheel with the surface of revolution of the workpiece,

e. a constant-torque motor system, and

f. connection means joining the output shaft of the motor to one of the elements to produce constant force engagement of the wheel and workpiece, said connection means being a rotary cam drivingly connected to said output shaft of the motor and having an operative surface that engages and slides relative to a pin extending from the said one of the elements.

4. A grinding machine as recited in claim 3, wherein sive wheel with the surface of revolution of the the pin extends horizontally, wherein the cam is rotatworkpiece, able about an axis spaced from and parallel to the pin, e. a constant-torque motor system, the motor system and wherein the operative surface of the cam is an inincluding a source of alternating current power, a clined ramp concentric with the cam axis and facing 5 capacitance, a motor, and connections joining the r the pin. power source, the capacitance, and the motor in S. A grinding machine for generating a surface of revseries. olution on a workpiece, comprising 6. A grinding machine as recited in claim 5, wherein a. a base, the motor system includes an inductance in series with b. a workhead element for carrying the workpiece 10 the capacitance, the inductance having a substantially mounted on the base, saturated core at currents in the normal range of operac. a wheelhead element having aspindle with an tion.

abrasive wheel mounted on the base, 7. A grinding machine as recited in claim 6, wherein d. way means permitting sliding motion transversely the motor armature is energized with DC from a rectiof the spindle axis between the workhead and the fier whose input is connected to the AC source. wheelhead to bring about engagement of the abra- 

1. A grinding machine for generating a surface of revolution on a workpiece, comprising a. a base, b. a workhead element for carrying the workpiece mounted on the base, c. a wheelhead element having a spindle with an abrasive wheel mounted on the base, d. way means permitting sliding motion transversely of the spindle axis between the workhead and the wheelhead to bring about engagement of the abrasive wheel with the surface of revolution of the workpiece, e. a constant-torque rotary motor system having a rotatable output shaft, the system including means to maintain the torque on the shaft at a predetermined value, and f. connection means joining the output shaft of the motor to one of the elements to produce constant force engagement of the wheel and workpiece.
 2. A grinding machine for generating a surface of revolution on a workpiece, comprising a. a base, b. a workhead element for carrying the workpiece mounted on the base, c. a wheelhead element having a spindle with an abrasive whEel mounted on the base, d. way means permitting sliding motion transversely of the spindle axis between the workhead and the wheelhead to bring about engagement of the abrasive wheel with the surface of revolution of the workpiece, e. a constant-torque motor system, and f. connection means joining the output shaft of the motor to one of the elements to produce constant force engagement of the wheel and workpiece, the said connection being a loop of cable having at least one wrap around the said output shaft of the motor, and the loop lying in a plane perpendicular to the said spindle axis, extending around four pulleys mounted on the base, and having one run between pulleys attached to the said one of the elements.
 3. A grinding machine for generating a surface of revolution on a workpiece, comprising a. a base, b. a workhead element for carrying the workpiece mounted on the base, c. a wheelhead element having a spindle with an abrasive wheel mounted on the base, d. way means permitting sliding motion transversely of the spindle axis between the workhead and the wheelhead to bring about engagement of the abrasive wheel with the surface of revolution of the workpiece, e. a constant-torque motor system, and f. connection means joining the output shaft of the motor to one of the elements to produce constant force engagement of the wheel and workpiece, said connection means being a rotary cam drivingly connected to said output shaft of the motor and having an operative surface that engages and slides relative to a pin extending from the said one of the elements.
 4. A grinding machine as recited in claim 3, wherein the pin extends horizontally, wherein the cam is rotatable about an axis spaced from and parallel to the pin, and wherein the operative surface of the cam is an inclined ramp concentric with the cam axis and facing the pin.
 5. A grinding machine for generating a surface of revolution on a workpiece, comprising a. a base, b. a workhead element for carrying the workpiece mounted on the base, c. a wheelhead element having a spindle with an abrasive wheel mounted on the base, d. way means permitting sliding motion transversely of the spindle axis between the workhead and the wheelhead to bring about engagement of the abrasive wheel with the surface of revolution of the workpiece, e. a constant-torque motor system, the motor system including a source of alternating current power, a capacitance, a motor, and connections joining the power source, the capacitance, and the motor in series.
 6. A grinding machine as recited in claim 5, wherein the motor system includes an inductance in series with the capacitance, the inductance having a substantially saturated core at currents in the normal range of operation.
 7. A grinding machine as recited in claim 6, wherein the motor armature is energized with DC from a rectifier whose input is connected to the AC source. 